This invention relates to a magnetic reluctance effect magnetic head and, more particularly, to an improvement in a connection structure of a forward side electrode.
A magnetic reluctance effect magnetic head employed in, for example, a playback magnetic head in, for example, a hard disc drive device, referred to herein as an MR head, comprises a lower magnetic pole 51 on which a magnetic sensitive area 53 is formed via a first insulating film 52 and an upper magnetic pole 55 formed on the magnetic sensitive area 53 via a second insulating film 54, as shown in FIG. 1. The magnetic sensitive area 53 is made up of a magnetic reluctance effect element 56, referred to herein as a MR element, having a forward side electrode 57 towards a surface 60 facing a magnetic recording medium and a rear electrode 58 on the opposite side, and a bias conductor 59 provided traversing the MR element 56 at right angles thereto for affording a bias magnetic field to the MR element 56 in a pre-set direction. A second insulating film 54 is interposed between the MR element 56 and the bias conductor 59.
With this type of the MR head, the upper magnetic pole 55 is thickened in the vicinity of the surface 60 facing the magnetic recording medium and the distance between the upper magnetic pole 55 and the lower magnetic pole 51 becomes narrow towards the surface 60 facing the magnetic recording medium. A terminal end portion 55a of the upper magnetic pole 55 and a terminal end portion 51a of the lower magnetic pole 51 face the MR element 56 via magnetic gap areas G each having a certain gap width. The terminal end portion 55a of the magnetic pole 55 is connected to a terminal electrode 57, with a connecting length L1 of the MR element 56 to a terminal electrode 57 directly being the depth of the magnetic gap. That is, the connecting length L1 of the MR element 56 with the terminal electrode 57 is set so as to be equal to the length L2 over which the terminal end portion 55a of the upper magnetic pole 55 faces the MR element 56 via the magnetic gap area G having a gap length g1.
For reproducing the information by the above-described MR head, the sense current is supplied to the MR element 56 from the forward side electrode 57 and the rear electrode 58, while a bias magnetic field is applied to the MR element 56 for magnetizing the MR element 56 in a pre-set direction. When the stray magnetic flux is supplied from the magnetic recording medium to the MR element 56, the direction of magnetization of the MR element is rotated due to the magnetic flux so that it has an angle related with the amount of the magnetic flux depending on the direction of the current flowing in the MR element 56. This causes the electrical resistance of the MR element 56 to be changed to produce voltage changes corresponding to the change in the electrical resistance across both terminals of the MR element. The information may be detected by detecting these voltage changes.
Although it is desired to improve the playback output with the above-described MR head, the playback output of the MR head is determined by the sensitivity of the MR element arranged in the magnetic sensitive area. Since the MR element is arranged in the MR head at right angles to the surface facing the magnetic recording medium, the closer a specified area of the MR element is to the surface facing the magnetic recording medium, the larger is the amount of the signal magnetic flux flowing into the MR element and hence the higher is the sensitivity of the specified area. However, the forward side electrode is provided on the surface of the MR element facing the magnetic recording medium, so that the portion of the MR element connected to the forward side electrode cannot be expected to exhibit the magnetic reluctance effects. Consequently, it has been desired to reduce the connecting length L1 between the MR element and the forward side electrode and to make use of the high sensitivity area in order to improve the sensitivity of the MR element and the playback output of the MR head.
On the other hand, it has also been desired to reduce the size and power consumption of the MR head device. If the connecting length L1 between the MR element and the terminal electrode is diminished to an excessively small value in order to improve the playback output as described above, the length L2 over which the upper magnetic pole and the MR element face each other with the magnetic gap area G therebetween is correspondingly diminished. However, if the facing length L2 is diminished, the bias current required for generating the optimum bias current is increased to render it difficult to realize the saving in power consumption.
Besides, in a hard disc device in which the MR head is used as playback means, plural hard discs are usually enclosed for increasing the recording capacity, so that plural MR heads are used in association with the hard discs. Since the same current may be used for these MR heads, the sense current is supplied via the same terminals to the MR heads. However, if the facing length L2 over which the upper magnetic pole and the MR element face each other via the magnetic gap area G is diminished, the dependency on the facing length L2 of the bias current required for generating the optimum bias magnetic field is increased, so that the amount of the required bias current becomes different due to the minute difference in the facing length L2. That is, it becomes impossible to supply the bias current for each of the MR heads via the same terminals. Consequently, different terminals for supplying the bias current are provided for the respective MR heads in the hard disc drive device, with the result that it becomes difficult to reduce the size of the device.
Also a part of the bias magnetic field generated by the bias conductor flows from the upper magnetic pole towards the lower magnetic pole so as to be applied to the MR element arranged between these poles. The portion of the MR element most strongly influenced by the bias magnetic field is the portion closer to the forward side electrode, that is the portion in which the upper magnetic pole is closest to the lower magnetic pole. It is in this region where magnetic saturation is most likely to occur. Consequently, with the conventional MR head, the portion of the MR element having the maximum sensitivity is not utilized so that the playback output is not optimum.